Expression of Giardia duodenalis β-Tubulin as a Soluble Protein in Escherichia coli☆

The β-tubulin gene of the parasitic protozoan Giardia duodenalis has been expressed for the first time using a novel and direct method. The protein was expressed in both soluble and insoluble forms in an Escherichia coli-based expression system. The level of expression was found to be affected by several variables including the incubation temperature, length of time for which expression was carried out, and the E. coli culture volume. The protein expression system contributed no additional amino acids to the final fusion protein and the polyhistidine fusion sequence was easily removed from the β-tubulin protein using a specific enterokinase enzyme. The expression system also provided a means of preparing a soluble protein and purifying it by a relatively straightforward affinity chromatography method to give a very high level of protein purity. This makes the protein suitable for a number of applications for characterization including β-tubulin antibody assays, α-/β-tubulin-binding regions, and β-tubulin folding intermediates.